refactor: remove date-fns && optimize code

package.json

@@ -48,7 +48,6 @@
     "vue": "^2.5.0"
   },
   "dependencies": {
-    "date-fns": "^2.0.1",
     "date-format-parse": "^0.2.5"
   },
   "devDependencies": {
@@ -62,7 +61,7 @@
     "@vue/babel-helper-vue-jsx-merge-props": "^1.0.0",
     "@vue/babel-preset-jsx": "^1.1.2",
     "@vue/component-compiler-utils": "^3.0.0",
-    "@vue/test-utils": "^1.0.0-beta.29",
+    "@vue/test-utils": "^1.1.1",
     "acorn": "^7.0.0",
     "autoprefixer": "^9.7.1",
     "babel-core": "^7.0.0-bridge.0",
@@ -72,6 +71,7 @@
     "core-js": "^3.3.5",
     "coveralls": "^3.0.7",
     "cross-env": "^6.0.3",
+    "date-fns": "^2.16.1",
     "eslint": "^6.2.2",
     "eslint-config-airbnb-base": "^14.0.0",
     "eslint-config-prettier": "^6.1.0",